Filled-gap magnetic recording head and method of making

ABSTRACT

A filled-gap magnetic recording head is provided comprising a flat or cylindrical contour head having a row of magnetic transducers in a gap region disposed between a rowbar substrate and a closure. The gap region is intentionally recessed to have a predetermined recess profile below a tape support surface. An electrical insulation layer is deposited on the tape support surface and on the recess profile of the gap region. The insulation layer prevents electrical shorting between the magnetic transducers and other conductive elements in the gap due to accumulations of conductive debris from the magnetic recording tape. A method of making the filled-gap magnetic recording head by intentionally recessing the gap region, cleaning the recessed profile and depositing an insulator layer is provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to magnetic tape recording heads, and moreparticularly, to a tape recording head having a pre-recessed gap regionfilled with an electrical insulation material.

2. Description of the Related Art

In magnetic storage systems, data is read from and written onto magneticrecording media utilizing magnetic transducers commonly referred to asmagnetic heads. Data is written on the magnetic recording media bymoving a magnetic recording head to a position over the media where thedata is to be stored. The magnetic recording head then generates amagnetic field, which encodes the data into the magnetic media. Data isread from the media by similarly positioning the magnetic read head andthen sensing the magnetic field of the magnetic media. Read and writeoperations may be independently synchronized with the movement of themedia to ensure that the data can be read from and written to thedesired location on the media.

An important and continuing goal in the data storage industry is that ofincreasing the density of data stored on a medium. For tape storagesystems, that goal has lead to increasing the track density on recordingtape, and decreasing the thickness of the magnetic tape medium. However,the development of small footprint, higher performance tape drivesystems has created various problems in the design of a tape headassembly for use in such systems.

In a tape drive system, magnetic tape is moved over the surface of thetape head at high speed. This movement generally entrains a film of airbetween the head and tape. Usually the tape head is designed to minimizethe spacing between the head and the tape. The spacing between themagnetic head and the magnetic tape is crucial so that the recordinggaps of the transducers, which are the source of the magnetic recordingflux, are in intimate or near contact with the tape to effect efficientsignal transfer, and so that the read element is in intimate or nearcontact with the tape to provide effective coupling of the magneticfield from the tape to the read element.

A flat contour thin film tape recording head for a bi-directional tapedrive is described in commonly assigned U.S. Pat. No. 5,905,613 toBiskeborn and Eaton. The flat contour head comprises a flat tape supportsurface on a substrate having a row of thin film transducers formed on asurface on one side of the substrate which forms a gap. The substratewith the row of transducers is called a “rowbar substrate”. Thetransducers are protected by a closure of the same or similar ceramic asthe substrate. For a read-while-write bi-directional head which requiresthat the read transducer follows behind the write transducer, two rowbarsubstrates with closures are mounted in a carrier opposing one another.The recording tape overwraps the corners of both substrates and closureswith an angle sufficient to scrape (skive) the air from the surface ofthe tape and not so large as to allow air to reenter between the tapeand the tape support surface after the tape passes the corner. Byscraping the air from the surface of the moving tape, a vacuum formsbetween the tape and the flat tape support surface holding the tape incontact with the tape support surface. At the corners of the air skivingedge, bending of the recording tape due to the overwrap results inseparation of the tape from the tape support surface for a distance thatdepends on the wrap angle, the tape thickness and the tape tension. Thetransducers must be spaced from the corners of the air skiving edges ata sufficient distance to allow the pressure difference between ambientair and the vacuum between the tape and the tape support surface toovercome this separation.

Recession of the gap region between the hard ceramic substrate andclosure due to tape wear is a problem that results in increased spacingloss of the readback signal. Efforts to minimize gap erosion in harddisk drive type ceramic tape heads usually involves making the gapmaterials more wear resistant or coating the head with wear resistantmaterial. Another problem that can occur is accumulation of conductivedebris and wear material in the recessed region that results inelectrical shorting of the magnetoresistive (MR) transducer elements inthe gap to other electrically conductive elements in the gap. Yetanother problem is corrosion of giant magnetoresistive (GMR) or magnetictunnel junction (MTJ) sensors when exposed directly to running tape.

The present invention addresses the need for a tape recording head thateliminates or reduces the harmful effects of accumulated conductivedebris to improve reliability and component life and that insulatesanisotropic magnetoresistive (AMR), GMR and MTJ sensors from electricalcharge exchange with the tape.

SUMMARY OF THE INVENTION

In accordance with the principles of the present invention, there isdisclosed an embodiment of filled-gap magnetic recording head comprisinga flat or cylindrical contour head having a row of magnetic transducersin a gap region disposed between a rowbar substrate and a closure. Thegap region is intentionally recessed to have a predetermined recessprofile below a tape support surface. An electrical insulation layer isdeposited on the tape support surface and on the recess profile of thegap region.

Another embodiment of a filled-gap magnetic recording head, according tothe invention, comprises a flat or cylindrical contour head having a rowof magnetic transducers in a gap disposed between a rowbar substrate anda closure. The gap is intentionally recessed to have a predeterminedrecess profile below a tape support surface. An electrical insulationlayer is deposited on the tape support surface and on the recess profileof the gap, the thickness of the insulating layer being approximatelyequal to or greater than the amount of intentional recession of the gap.The tape support surface is lapped to reduce the thickness of theinsulator layer to be approximately equal to the amount of recession ofthe gap or, alternatively, lapped back to the original tape supportsurface.

A method of making the filled-gap magnetic recording head comprisessupplying a recording head having a tape support surface including a gapdisposed between a rowbar substrate and a closure, intentionallyrecessing the gap by running a chromium oxide tape over the tape supportsurface, sputter cleaning the head in a vacuum, depositing an electricalinsulation layer on the tape support surface surface and recessed gap,and if desired lapping the tape support surface to reduce the thicknessof the insulation layer on the tape supporting regions.

The above as well as additional objects, features, and advantages of thepresent invention will become apparent in the following detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the presentinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings. In the following drawings, like referencenumerals designate like or similar parts throughout the drawings:

FIG. 1 is a cross-sectional view, not to scale, of a read-while-writebi-directional flat contour linear tape recording head;

FIG. 2 is a perspective view, not to scale, of a rowbar substrate andclosure assembly incorporating the present invention;

FIG. 3 a is a cross-sectional view, not to scale, of the gap region ofthe rowbar substrate and closure assembly after lapping;

FIG. 3 b is a top view, not to scale, of one read-write transducerportion of the gap region of FIG. 3 a.

FIG. 3 c is a cross-sectional view, not to scale, of the gap region ofthe rowbar substrate and closure assembly after a forced recessionprocess;

FIG. 3 d is a cross-sectional view, not to scale, of an embodiment ofthe gap region of the rowbar substrate and closure assembly afterdeposition of a layer of insulation material;

FIG. 4 a is a cross-sectional view, not to scale, of another embodimentof the gap region of the rowbar substrate and closure assembly afterdeposition of a layer of insulation material;

FIG. 4 b is a cross-sectional view, not to scale, of the gap region ofthe rowbar substrate and closure assembly of FIG. 4 a after lapping;

FIG. 5 is a flow chart of a method of making a filled-gap magneticrecording head according to the present invention; and

FIG. 6 is a simplified diagram of a magnetic tape recorder system usingthe magnetic recording head of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a bi-directional read-while-write flat contour head100 using the present invention. Rowbar substrates 102 and 104 of a wearresistant material, such as the substrate ceramic typically used inmagnetic disk drive heads, are mounted in carriers 105 and 106 fixed ata small angle α with respect to each other. The ceramic rowbarsubstrates 102 and 104 are provided with flat tape support surfaces 108and 110 and gap surfaces 109 and 111 and a row of transducers at thesurfaces of gap regions 112 and 114. Electrical connection cables 116and 118 connect the transducers to the read/write channel of theassociated tape drive. The wrap angle θ of the tape 120 at edges 122 and124 going onto the flat tape support surfaces 108 and 110, respectively,and angle α/2 are usually between ⅛ degree and 4.5 degrees. The rows oftransducers are protected by closures 130 and 132 made of the same orsimilar ceramic as the rowbar substrates 102 and 104.

FIG. 2 is a perspective view of a rowbar substrate and closure assembly200 comprising the rowbar substrate 102, the closure 130 and the gapregion 112 shown in FIG. 1. The assembly 200 has a length L₁ greaterthan the width of the magnetic recording tape 120 extending in directionperpendicular to the direction of the linear motion of the tape acrossthe head 100. The flat tape support surface 108 supports the tape as itmoves across the head. A row of transducers 202 positioned in the gapregion 112 and having a length L₂ less than the width of the tape iscentered along the length direction of the assembly 200. The row oftransducers 202 comprises a plurality of read and write transducers forreading and writing data on the magnetic recording tape. Servo readtransducers which may be located at first and second ends 204 and 206 ofthe row of transducers 202 are used to position the read and writetransducers over data tracks written on the magnetic recording tape.

FIGS. 3 a, 3 c and 3 d are cross-sectional views of the gap 112 ofassembly 200 illustrating the structure of the gap region at variousstages of fabrication of the filled-gap recording head of the invention.FIG. 3 a shows sections A-A indicated on FIG. 2 as area 300 through themiddle region of the rowbar substrate and closure assembly 200 near thetape support surface 108 where the row of transducers 202 are present.FIG. 3 b is a top view of one read-write transducer portion of the gapregion of FIG. 3 a. The gap 112 comprises an undercoat 302 of aluminumoxide, a read transducer 304, an insulation layer 306 of aluminum oxide,a write transducer 308 and an overcoat 310 of aluminum oxide sandwichedbetween the rowbar substrate 102 and the closure 130. These elements areformed on the rowbar substrate surface 312 by wafer deposition methodswell known to those skilled in the art. Closure 130 is then fixed to theovercoat 310 to protect the transducers in the gap region. Typically,the gap 112 has a width W of about 30-35 microns. The read transducer304 comprises an MR transducer sandwiched between first and secondshields S₁ and S₂, respectively, formed of a soft magnetic material suchas permalloy. The MR transducer, which may be an anisotropicmagnetoresistance (AMR) sensor, a giant magnetoresistance (GMR) sensoror a tunneling magnetoresistance (TMR) sensor, is electrically insulatedfrom S₁ and S₂ by insulator layers 316 and 318 formed of aluminum oxide.The write transducer 308 comprises a write gap 320 formed of nonmagneticmaterial between first and second write poles P₁ and P₂, respectively,formed of soft magnetic material such as permalloy. After the depositionof the layers comprising the gap 112 and attachment of the protectiveclosure 130, the tape support surface 108 is lapped to obtain thedesired poletip dimensions of poles P1 and P2 and a flat or cylindricalsurface finish. The gap region 300 of the fabrication stage shown inFIG. 3 a is essentially equivalent to the completed gap region ofconventional tape recording heads.

FIG. 3 c is a cross-sectional view of the gap 112 of assembly 200 aftera forced recession process step has been completed on the gap structureshown in FIG. 3 a. The gap 112 has been intentionally recessed below thetape support surface 108 to create a uniformly recessed gap profile 322.The recession δ of the recessed gap profile 322 from the tape supportsurface 108 in the range of 20-50 nm is achieved by running a chromiumoxide recording tape over the tape support surface of the recordinghead. Etching by the chromium oxide recording tape is not selective andhas been found to etch all the gap components at approximately the samerate creating a very uniform recessed gap profile. The desired recessionproduced by this process should be approximately equivalent to therecession asymptote due to long term tape wear of a conventional headunder normal operating conditions. This recession has been found to beeasily achieved by running two round trips of an 85 meter length ofchromium oxide tape over the head. Alternatively, other tapes includingchrome, diamond and aluminum oxide, may be used to intentionally recessthe gap 112.

Alternatively, ion milling, sputtering, chemical-mechanical lapping,grinding and sputtering processes may be used to intentionally recessthe gap 112. Sputtering is less attractive since sputtering rates differfor different materials leading to selective etching of the gapcomponents. Because of the small dimensions of the gap region and thedesired recession δ, grinding would require a very high precisionprocess which may be difficult to implement.

After the intentional recession of the gap 112 by conditioning with thechromium oxide tape is completed, the head is placed in a vacuum systemwhere it is sputter cleaned in an argon-hydrogen plasma for less than 1minute to remove residual debris and other contamination from therecessed gap profile 322. If selective pole tip etching is desired alonger sputter clean time may be used. After cleaning, an electricallyinsulating layer 324 having a thickness in the range of 4-20 nm isdeposited on the tape support surface 108 and the recessed gap as shownin FIG. 3 d. Insulating layer 324 is preferably a hard stoichiometricfilm of aluminum oxide or other similar material including low stressdiamond-like carbon (DLC), silicon nitride, boron nitride, siliconcarbide and silicon oxide. The requirement for the insulation layer 324is that it is wear resistant, but not necessarily wear proof as a lowwear rate is acceptable. Running tape on the head may wear theinsulation layer 324 of the tape support surface 108, however the wearrate of the insulation layer in the gap 112 is slow due to the recessionδ of the gap profile 322. Insulation layers 324 thinner than 4-10 nm arepossible if pinholes are not a problem. Thicker insulation layers 324are generally not desirable due to initial head tape separation whichadds to the gap recession. Over the life of the head, the MR transducer314 is protected by the insulation layer 324 from shorting to conductivecomponents, including the shields S₁ and S₂, the poles P₁ and P₂, therowbar substrate 102 and the closure 130, by accumulations of conductivematerial from the recording tape 120 or by ductile motion (smearing) ofhead metallic components. The insulation layer also serves a secondarypurpose of protecting sensitive transducers, such as GMR and TMRtransducers, from direct contact with the tape which may result infailure of the transducers.

Alternatively, after the intentional recession of the gap 112 byconditioning with the chromium oxide tape, the head may be used in atape drive without deposition of the insulator layer 324. However, toobtain the full benefit of recession of the gap 112, deposition of theinsulator layer provides additional protection from shorting of the MRtransducer by accumulated conductive debris.

FIGS. 4 a and 4 b illustrate another embodiment of the filled-gapmagnetic recording head of the present invention described withreference to FIGS. 2 and 3 a-3 c. The embodiment shown in FIGS. 4 a and4 b is the same as the embodiment shown in FIGS. 3 a-3 c except thatafter sputter cleaning of the intentionally recessed gap 112 asdescribed herein above, an insulation layer 402 thick enough to fill thegap 112 approximately to the level of the tape support surface 108 isdeposited on the tape support surface 108 and the surface of therecessed gap profile 322. FIG. 4 a is a cross-sectional view of the area300 of the gap 112 of assembly 200 after deposition of the insulationlayer 402. FIG. 4 b is a cross-sectional view of the area 300 after alapping process of the tape support surface of the rowbar substrate andsubstrate assembly to reduce the thickness of the insulation layer 402to the level, or very nearly to the level of the tape support surface108 of the rowbar substrate 102 and the closure 130. Lapping of theassembly may be done by kiss lapping or by chemical-mechanical polishingmethods known to the art.

FIG. 5 is a flow chart of a method 500 of making a filled-gap magneticrecording head according to the present invention. In step 502, amagnetic tape head 100 having a lapped transducing surface 108 issupplied. In step 504, the gap region 112 of the rowbar substrate andclosure assembly 200 is intentionally recessed an by an amount δ in therange of 20-50 nm below the tape support surface 108, preferably byrunning a chromium oxide tape over the tape support surface. In step506, the rowbar substrate and closure assembly 200 is placed in a vacuumand the tape support surface 108 and recessed gap profile 322 is sputtercleaned, preferably in an argon-hydrogen plasma. In step 508, aninsulation layer 324 is deposited by vacuum deposition methods on thetape support surface 108 and on the surface of the recessed gap profile322. The deposited insulation layer may have a thickness less than therecession δ, preferably in the range of 4-20 nm, or alternatively mayhave a thickness greater than the recession δ. In step 510, a decisionis made whether or not to reduce the thickness of the insulation layer324. If reducing the thickness of the deposited insulation layer 324 isnot desired the process ends at step 516. If it is desired to reduce thethickness the insulation layer deposited on the tape support surface 108of the rowbar substrate 102 and closure 130, for example, as illustratedin FIG. 4 a, in step 512 the tape support surface 108 of the assembly200 is lapped, preferably by a kiss-lapping process to reduce thethickness of the insulation layer on the tape support surface 108 thedesired amount. Preferably, the thickness of the insulation layer on thetape support surface 108 is small to prevent a significant increase ofthe recording tape-transducer separation in the recessed gap region. Theprocess is then ended at step 516.

A novel feature of the present invention is providing a forced orintentional recession by a predetermined amount δ creating a gap profile322 prior to the deposition of an electrical insulation layer 324. Theelectrical insulation layer in the gap 112 is less exposed to wear bythe recording tape 120 for the duration of the head lifetime whileavoiding the problem of excessive spacing of the recording tape from theread and write transducers. The insulation layer eliminates MRtransducer resistance reduction and resistance fluctuations caused byaccumulations of conductive materials from the magnetic recording tapewhich can result in tape drive field failures.

FIG. 6 illustrates an embodiment of a magnetic tape recorder or tapedrive system 600 incorporating the filled-gap magnetic recording head ofthe present invention. A tape drive control unit 602 provides a motorcontrol signal to rotate tape reels 604 and move magnetic tape 606across the read/write transducer head 601. Read/write channel 608transmits read/write signals between the read/write transducer 601 andthe control unit 602. The data is communicated through I/O channel 610with host 612. Lateral positioning of the transducer 601 with respect tothe tape 606 is accomplished by positioning actuator 614. The lateralrepositioning is required to access the various tracks of the tape 606with the transducer 601. A servo system may be employed for accuratelateral repositioning of the transducer 601. An exemplary servo systemincludes a servo detector 616 to detect both the track that the head iscurrently on and whether the head is off center. Control unit 602indicates the track address of a desired new track to position errordetection controller 618 for repositioning the head. Servo detector 616indicates the current track to position error detection controller 618,and the controller provides a servo position error signal to positioningactuator 614 which repositions the transducer 601 to the new track. Theservo system also provides track following signals to positioningactuator 614 so that the tracks on tape 606 may be closely spaced.

While the present invention has been particularly shown and describedwith reference to the preferred embodiments, it will be understood bythose skilled in the art that various changes in form and detail may bemade without departing from the spirit, scope and teaching of theinvention. Accordingly, the disclosed invention is to be consideredmerely as illustrative and limited only as specified in the appendedclaims.

1. A magnetic head comprising: a rowbar substrate having a tape support surface and a gap surface at a substrate edge; a gap having a transducer row with at least one magnetoresistive (MR) sensor on the gap surface of the rowbar substrate, said gap having a gap profile recessed from the tape support surface; a closure covering the gap on a side thereof opposite the gap surface of the rowbar substrate, said closure forming a portion of the tape support surface; and an insulator layer over the tape support surface and the recessed gap profile.
 2. The magnetic head recited in claim 1, wherein the gap profile is recessed in the range of 10-50 nm from the tape support surface.
 3. The magnetic head recited in claim 1, wherein the insulator layer has a thickness in the range of 4-20 nm.
 4. The magnetic head recited in claim 1, wherein the insulator layer has a thickness approximately equal to the thickness of the recession of the gap profile from the tape support surface.
 5. The magnetic head recited in claim 1, wherein the insulator layer is chosen from the group of materials consisting of aluminum oxide, silicon nitride, boron nitride, silicon carbide, silicon oxide and diamond-like carbon.
 6. The magnetic head, recited in claim 1, wherein the gap profile is recessed by conditioning with a chromium oxide tape.
 7. A magnetic head comprising: a rowbar substrate having a tape support surface and a gap surface; a gap comprising at least one MR transducer on the gap surface of the substrate, said gap forming a recessed portion of the tape support surface; a closure covering the gap on a side thereof opposite said gap surface, said closure forming a further portion of the tape support surface; and an insulator layer on the recessed portion of the tape support surface.
 8. The magnetic head recited in claim 7, wherein the gap profile is recessed in the range of 10-50 nm from the tape support surface.
 9. The magnetic head recited in claim 7, wherein the insulator layer has a thickness in the range of 4-20 nm.
 10. The magnetic head recited in claim 7, wherein the insulator layer has a thickness approximately equal to the thickness of the recession of the gap profile from the tape support surface.
 11. The magnetic head recited in claim 7, wherein the insulator layer is chosen from the group of materials consisting of aluminum oxide, silicon nitride, boron nitride, silicon carbide, silicon oxide and diamond-like carbon.
 12. The magnetic head, recited in claim 7, wherein the gap profile is recessed by conditioning with a chromium oxide tape.
 13. A method of making a magnetic head comprising: supplying a magnetic recording head having a gap disposed between a rowbar substrate and a closure, said rowbar substrate and closure having a tape support surface; recessing the gap below the level of the tape support surface; sputter cleaning the head in a vacuum; and depositing an insulation layer on the tape support surface and the recessed gap.
 14. The method of making a magnetic head recited in claim 13, wherein the gap profile is recessed in the range of 10-50 nm from the tape support surface.
 15. The method of making a magnetic head recited in claim 13, wherein the insulator layer has a thickness in the range of 4-20 nm.
 16. The method of making a magnetic head recited in claim 13, wherein the insulator layer is deposited to have a thickness approximately equal to the recession of the gap profile from the tape support surface.
 17. The method of making a magnetic head recited in claim 13, wherein the insulator layer is chosen from the group of materials consisting of aluminum oxide, silicon nitride, boron nitride, silicon carbide, silicon oxide and diamond-like carbon.
 18. The method of making a magnetic head recited in claim 13, wherein the gap profile is recessed by conditioning with a chromium oxide tape.
 19. The method of making a magnetic head recited in claim 16, including lapping the tape support surface to reduce the thickness of the deposited insulator layer.
 20. A magnetic tape recorder system comprising: a magnetic recording tape; a tape drive for moving the magnetic recording tape linearly and bidirectionally; a magnetic head for magnetically recording data on the magnetic recording tape and for sensing magnetically recorded data on the magnetic recording tape, said magnetic head comprising: a rowbar substrate having a tape support surface and a gap surface at a substrate edge; a gap having a transducer row with at least one magnetoresistive (MR) sensor on the gap surface of the rowbar substrate, said gap having a gap profile recessed from the tape support surface; a closure covering the gap on a side thereof opposite the gap surface of the rowbar substrate, said closure forming a portion of the tape support surface; and an insulator layer over the recessed gap profile; an actuator for positioning said magnetic head to access various tracks on the magnetic recording tape; and a read/write channel coupled electrically to the magnetic head for magnetically recording data on the magnetic recording tape and for reading data recorded on the magnetic recording tape.
 21. The magnetic tape recorder system recited in claim 20, wherein the insulator layer is chosen from the group of materials consisting of aluminum oxide, silicon nitride, boron nitride, silicon carbide, silicon oxide and diamond-like carbon.
 22. The magnetic tape recorder system recited in claim 20, wherein the gap profile is recessed in the range of 10-50 nm from the tape support surface. 